package com.liehacker.android.util;

import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

public class AESCrypto {
	
	
	private String iv = "fedcba9876543210";
    private IvParameterSpec ivspec;
    private SecretKeySpec keyspec;
    private Cipher cipher;    
    private String SecretKey = "0123456789abcdef";
		
    public AESCrypto()
    {
            ivspec = new IvParameterSpec(iv.getBytes());

            keyspec = new SecretKeySpec(SecretKey.getBytes(), "AES");
            
            try {
                    cipher = Cipher.getInstance("AES/CBC/NoPadding");
            } catch (NoSuchAlgorithmException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
            } catch (NoSuchPaddingException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
            }
    }
    
    public String encryptAES(String text) throws Exception
    {
            if(text == null || text.length() == 0)
                    throw new Exception("Empty string");
            
            byte[] encrypted = null;

            try {
                    cipher.init(Cipher.ENCRYPT_MODE, keyspec, ivspec);

                    encrypted = cipher.doFinal(padString(text).getBytes());
            } catch (Exception e)
            {                       
                    throw new Exception("[encrypt] " + e.getMessage());
            }
            
            return toHex(encrypted);
    }
    
    public String decryptAES(String code) throws Exception
    {
            if(code == null || code.length() == 0)
                    throw new Exception("Empty string");
            
            byte[] decrypted = null;

            try {
                    cipher.init(Cipher.DECRYPT_MODE, keyspec, ivspec);
                    
                    decrypted = cipher.doFinal(hexToBytes(code));
            } catch (Exception e)
            {
                    throw new Exception("[decrypt] " + e.getMessage());
            }
            return fromHex(toHex(decrypted));
    }
    
    public String bytesToHex(byte[] data)
    {
            if (data==null)
            {
                    return null;
            }
            
            int len = data.length;
            String str = "";
            for (int i=0; i<len; i++) {
                    if ((data[i]&0xFF)<16)
                            str = str + "0" + java.lang.Integer.toHexString(data[i]&0xFF);
                    else
                            str = str + java.lang.Integer.toHexString(data[i]&0xFF);
            }
            return str;
    }
            
    public static byte[] hexToBytes(String str) {
            if (str==null) {
                    return null;
            } else if (str.length() < 2) {
                    return null;
            } else {
                    int len = str.length() / 2;
                    byte[] buffer = new byte[len];
                    for (int i=0; i<len; i++) {
                            buffer[i] = (byte) Integer.parseInt(str.substring(i*2,i*2+2),16);
                    }
                    return buffer;
            }
    }   

    private static String padString(String source)
    {
      char paddingChar = ' ';
      int size = 16;
      int x = source.length() % size;
      int padLength = size - x;

      for (int i = 0; i < padLength; i++)
      {
              source += paddingChar;
      }

      return source;
    }
	
	
	private static final String CRYPTO_SEED_PASSWORD = "!t@v#i$n";
	
	public static String encrypt(String cleartext) throws Exception
	{
		byte[] rawKey = getRawKey(CRYPTO_SEED_PASSWORD.getBytes());
		byte[] result = encrypt(rawKey, cleartext.getBytes());
		return toHex(result);
	}
	
	public static String decrypt(String encrypted) throws Exception
	{
		byte[] rawKey = getRawKey(CRYPTO_SEED_PASSWORD.getBytes());
		byte[] enc = toByte(encrypted);
		byte[] result = decrypt(rawKey, enc);
		return new String(result);
	}

	private static byte[] getRawKey(byte[] seed) throws Exception
	{
		KeyGenerator kgen = KeyGenerator.getInstance("AES");
		SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
		sr.setSeed(seed);
	    kgen.init(128, sr); // 192 and 256 bits may not be available
	    SecretKey skey = kgen.generateKey();
	    byte[] raw = skey.getEncoded();
	    return raw;
	}

	
	private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception
	{
	    SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
		Cipher cipher = Cipher.getInstance("AES");
	    cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
	    byte[] encrypted = cipher.doFinal(clear);
		return encrypted;
	}

	private static byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception
	{
	    SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
		Cipher cipher = Cipher.getInstance("AES");
	    cipher.init(Cipher.DECRYPT_MODE, skeySpec);
	    byte[] decrypted = cipher.doFinal(encrypted);
		return decrypted;
	}

	public static String toHex(String txt)
	{
		return toHex(txt.getBytes());
	}
	
	public static String fromHex(String hex)
	{
		return new String(toByte(hex));
	}
	
	public static byte[] toByte(String hexString)
	{
		int len = hexString.length()/2;
		byte[] result = new byte[len];
		for (int i = 0; i < len; i++)
			result[i] = Integer.valueOf(hexString.substring(2*i, 2*i+2), 16).byteValue();
		return result;
	}

	public static String toHex(byte[] buf)
	{
		if (buf == null)
			return "";
		StringBuffer result = new StringBuffer(2*buf.length);
		for (int i = 0; i < buf.length; i++) {
			appendHex(result, buf[i]);
		}
		return result.toString();
	}
	
	private final static String HEX = "0123456789ABCDEF";
	private static void appendHex(StringBuffer sb, byte b)
	{
		sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f));
	}
	
}
